Chapter 3 Observational Studies and Experiments

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CHAPTER 3
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Chapter 3Observational Studies and Experiments

• DEFINITIONS Page 147
• In a designed experiment,
• the researcher actively imposes some treatment on
  the units or subjects in order to observe the
  responses.
• In an observational study,
• the researcher simply observes the subjects or
  units and records variables of interest. The
  researcher does not attempt to manipulate or
  influence the responses.

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DEFINITIONSpage 152

• A confounding variable is a variable whose effect
  on the response variable cannot be separated from
  the effect of the explanatory variable on the
  response variable. It is a variable that offers
  an alternative explanation for the results of the
  study.

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DEFINITIONSPage 174

• A treatment group
• is a group of subjects or experimental units
  that receive an actual treatment.
• A control group
• is a group of subjects or experimental units
  that are treated identically in every way, except
  that they do not receive an actual treatment. In
  some experiments, the control group receives a
  standard or existing treatment that the new
  treatment will be compared to. A special kind of
  control group is one that receives a placebo
  treatment (more on placebos on page 000).

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DEFINITIONSPage 176

• The placebo effect is phenomenon that receiving
  medical attention, even administration of an
  inert drug, improves the condition of the
  subjects.
• Experimenter bias is the distortion that can
  arise on the part of the experimenter due to how
  the subjects are assigned to the groups, which
  variables are measured and how they are measured,
  how the results are interpreted. The bias is
  generally in the direction of the researchers
  theory.
• A single-blind experiment is one in which the
  subjects are ignorant of which treatment they
  receive. A double-blind experiment is one in
  which neither the subjects nor those working with
  the subjects knows who is receiving which
  treatment.

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• LDI 3.1, 3.2, 3.5, 3.9